Question

BSA was injected into a rabbit as antigen and polyclonal antibody was obtained. From this polyclonal antisera, IgG fraction was purified by standard methods. If the same lot of IgG polyclonal antibodies are digested either with pepsin or papain and subsequently incubated with the antigen (BSA), which of the following outcomes will be true?

• A. Pepsin digested IgG will precipitate the antigen.
• B. Papain digested antibody will precipitate the antigen.
• C. Both the antibody will precipitate antigen.
• D. None of them will precipitate.

Answer 1

The correct option is A Pepsin digested IgG will precipitate the antigen.

The digestion of the antibody IgG molecule can be carried out with the help of pepsin and papain. The pepsin causes breaking of the molecule near the hinge which creates the divalent molecules as the Fab fragment are joined together. It can crosslink with the antigens and will result in precipitation. The papain enzyme digests the IgG and produces monovalent by breaking the two Fab fragment which cannot crosslink the antigen and will not cause precipitation.

Thus, the correct answer is option A.